Seat track assembly for a motor vehicle having an integrated position sensor

ABSTRACT

A seat track assembly for a seat of a motor vehicle having a floor and an airbag. The seat track assembly includes a stationary rail fixedly secured to the floor. The seat track assembly also includes a movable rail fixedly secured to the seat and slidably engaged with the stationary rail to move the seat therealong. The movable rail extends along a length between a forward position and a rearward position. A shunt defining an elongated body extends along a portion of the length of the movable rail. A sensor is fixedly secured to the stationary rail and disposed adjacent the shunt to produce a position signal indicating a position of the sensor relative to the shunt. The sensor and the shunt are disposed within the stationary and movable rails to be protected thereby.

RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.10/484,365 filed on Jul. 9, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a seat track assembly for seat of a motorvehicle. In particular, this invention relates to a seat track assemblyhaving a sensor integrated into a track system thereof for identifying aplurality of positions for the seat.

2. Background of the Invention

A seat track assembly extends along a floor of a motor vehicle andsupports a seat thereabove. Typically, the seat track assembly includesa stationary rail secured to a floor and a movable rail secured to theseat. The movable rail slidingly engages the stationary rail to move theseat between a plurality of positions. The plurality of positions allowsthe seat to be adaptable for use by persons of different heights. Forexample, the seat may be moved to a forward position closer to asteering wheel to give a driver greater control over the steering wheelor to allow the driver to reach the control pedals with their feet.Alternatively, the seat may be moved to the forward position to createextra cargo space behind the seat or to accommodate taller occupants ofa rear seat.

The position of the seat can influence the effectiveness of an airbagsystem. Airbag systems, which include an airbag stored in a housing, areinstalled throughout a passenger compartment to absorb a collision shockcreated upon motor vehicle impact. For example, the airbag can be storedwithin the steering wheel or an instrument panel for the safety of anoccupant of the motor vehicle. The airbag inflates with gas in responseto a signal generated by a sensor upon motor vehicle impact. Typically,the inflation of the airbag occurs at a high deployment rate so that theairbag is deployed immediately upon motor vehicle impact. But when theseat is in the forward position, a lower deployment rate is desired toreduce the risk of injury to the occupant thereof.

Systems to control the deployment rate of the airbag based upon theposition of the seat are known to those skilled in the art. U.S. Pat.No. 6,053,529 to Frusti et al. discloses a deployable passengerrestraint system for a motor vehicle having a seat mounted on a seattrack assembly. The seat track assembly includes a movable rail thatslides relative to a stationary rail. The system includes a sensorflange having a predetermined length secured along an outer surface ofthe movable rail, and a sensor extending out from the stationary rail.As the movable rail slides along the stationary rail to move the seat,the sensor detects the absence or presence of the sensor flange andgenerates a signal representing the position of the seat. The signal issent to a processor, which increases or decreases the deployment rate ofa deployable restraint depending upon the position of the seat.

SUMMARY OF THE INVENTION

A seat track assembly for a seat of a motor vehicle having a floor andan airbag includes a stationary rail fixedly secured to the floor. Theseat track assembly also includes a movable rail fixedly secured to theseat and slidably engaged with the stationary rail to move the seattherealong. The movable rail extends along a length between a forwardposition and a rearward position. A shunt defining an elongated bodyextends along a portion of the length of the movable rail. A sensor isfixedly secured to the stationary rail and disposed adjacent the shuntto produce a position signal indicating a position of the sensorrelative to the shunt. The sensor and the shunt are disposed within thestationary and movable rails to be protected thereby.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the invention will be readily appreciated as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanying drawingswherein:

FIG. 1 is a side schematic view of a seat and a seat track assemblypositioned within a passenger compartment of a motor vehicle;

FIG. 2 is a side view, partially exploded and cut away, of a seat trackassembly of one embodiment of the invention; and

FIG. 3 is a cross-sectional view taken along lines 3-3 of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the Figures, a seat, generally shown at 10, is positionedwithin a passenger compartment 12 of a motor vehicle 14. The seat 10includes a seat cushion 16, a seat back 18, and a head restraint 20 forsupporting an occupant of the motor vehicle 14 thereon. Although theseat 10 shown in FIG. 1 is a driver side front seat, it is contemplatedthat the description below is equally applicable to a passenger sidefront seat or to additional seats positioned throughout the passengercompartment 12.

A seat track assembly, generally indicated at 22, extends along a floor24 of the motor vehicle 14 and supports the seat 10 thereabove. The seattrack assembly 22 allows for movement of the seat 10 between a forwardposition, in which the seat 10 is in close proximity to a steering wheel26, a rearward position, in which the seat 10 is away from the steeringwheel 26, and various intermediate positions therebetween. Movement ofthe seat 10 allows the seat 10 to be adaptable for occupants ofdifferent heights. For example, the seat 10 may be moved to the forwardposition to allow a driver to reach control pedals (not shown) withtheir feet. In addition, the seat 10 may be moved to the forwardposition to create extra cargo space behind the seat 10, or toaccommodate taller occupants of rear seats (not shown). Movement of theseat 10 may be achieved manually or through a power system (not shown).

The seat track assembly 22 includes a stationary rail 28 and a movablerail 30. The stationary rail 28 is fixedly secured to the floor 24 by aplurality of floor brackets 32. The stationary rail 28 includes innersides 34 and a lower cross member 36 extending between the inner sides34. Each of the inner sides 34 defines an arcuate end 38 for engagingthe movable rail 30 to slide the seat 10 therealong.

The movable rail 30 is fixedly secured to the seat 10 by seat brackets40. The movable rail 30 extends along a length between a forwardposition and a rearward position. The movable rail 30 includes outersides 42 and an upper cross member 44 extending between the outer sides42. The outer sides 42 define U-shaped ends 46, which engage the arcuateend 38 of the inner sides 32 as the movable rail 30 slides along thestationary rail 28. A stop 48 extends down from the movable rail 30 tolimit movement thereof relative to the stationary rail 28.

A shunt, generally shown at 50, defines an elongated body 52 extendingalong a portion of the length of the movable rail 30. The shunt 50 isfixedly secured to the upper cross member 44 by a securing flange 54.Rivets 56 hold the securing flange 54 to the upper cross member 44. Theshunt 50 is positioned between the outer sides 42 of the movable rail30. This positioning protects the shunt 50 from wear and tear that mightotherwise cause weakening of the attachment of the shunt 50 to themovable rail 30.

The shunt 50 includes a ferromagnetic surface 58 and a non-ferromagneticsurface 60 extending along the elongated body 52. The shunt 50 definesan interface 59 where the ferromagnetic surface 58 and thenon-ferromagnetic surface 60 meet. In the embodiment shown in theFigures, the ferromagnetic surface 58 extends along approximately fortypercent (40%) of the elongated body 52 and the non-ferromagnetic surface60 extends along approximately sixty percent (60%) of the elongated body52. The percentages of the ferromagnetic surface 58 and thenon-ferromagnetic surface 60 will, however, vary depending on thespecific implementation of the invention.

In the preferred embodiment, the shunt 50 has a thin steel support 62extending therealong. The steel support 62 is used for the ferromagneticsurface 58. The non-ferromagnetic surface 60 is a thermoplastic materialthat is molded over the steel support 62. It should be appreciated bythose skilled in the art that the steel support 62 does not have toextend along the entire shunt 50, and that the non-ferromagnetic surface60 may be fabricated to support itself.

A sensor 64 is operatively secured to the stationary rail 28. The sensor64 is an Optek Hall effect sensor having a U-shape configuration whenviewed from the end shown in FIG. 3. The sensor 64 measures the magneticfield strength surrounding it. The sensor 64 includes a sensor crossmember 68 and sensor sides 66 extending perpendicularly therefrom. Thesensor sides 66 extend up on either side of the shunt 50 so that thesensor 64 is disposed adjacent the shunt 50.

Depending on where the sensor 64 is along the length of the shunt 50will determine the strength of the magnetic field which will, in turn,identify the position of the seat 10. A sensor bracket 70, which ispreferably a stamped metal bracket, holds the sensor sides 66 and thesensor cross member 68 in place relative to each other. The sensorbracket 70 also fixedly secures the sensor 64 to the lower cross member36 so that the sensor 64 is disposed within the inner sides 34 of thestationary rail 28. Thus, the sensor 64 is protected from theenvironment outside of the seat track assembly 20.

Alternatively, it will be appreciated that the shunt 50 can be securedwithin the stationary rail 28 so that the elongated body 52 extendsalong a portion of a length thereof, and that the sensor 64 can besecured within the movable rail 30.

A wire harness 72 is secured to the sensor 64 with fasteners 74. Thewire harness 72 provides power to the sensor 64 from a power source (notshown). In the embodiment shown, the fasteners 74 are bolts that aretightened in place using nuts 78. It should be appreciated by thoseskilled in the art that any fastener that is capable of withstanding theenvironment may be used in place of the bolts 74 and the nuts 78. Thesensor 64 and the fasteners 74 must be secure enough co act as alimiter. More specifically, the sensor 64 will abut the stop 48 toprevent the movable rail 30 from moving therepast.

In operation, when the sensor 64 senses the presence of theferromagnetic surface 58, the sensor 64 will transmit the positionsignal through a signal conductor in the wire harness 72 to a controller76. Depending on how the controller 76 is programmed, the positionsignal will identify the seat 10 as being forward or rearward of aposition identified by the interface 59 where the ferromagnetic surface58 meets the non-ferromagnetic surface 60. As should be appreciated bythose skilled in the art, the position signal is either present or not,i.e., a digital signal, and to what seat position (forward or rearward)the position signal is assigned to is a design choice.

If the seat 10 is identified as being in the forward position, thecontroller 76 transmits a control signal to an airbag controller 80,which will then generate an airbag control signal to reduce thedeployment rate of an airbag 82. Conversely, if the seat 10 isidentified as being in the rearward position, the controller 76 willtransmit a control signal to the airbag controller 80, which will thengenerate an airbag control signal to increase the deployment rate of theairbag 82.

Although the foregoing description has been described in relation to theseat 10 of a motor vehicle 14, it will be readily apparent to thoseskilled in the art that the invention could be installed in conjunctionwith any type of seat for any vehicle.

The invention has been described in an illustrative manner. It is to beunderstood that the terminology, which has been used, is intended to bein the nature of words of description rather than of limitation.

Many modifications and variations of the invention are possible in lightof the above teachings. Therefore, within the scope of the appendedclaims, the invention may be practiced other than as specificallydescribed.

1-24. (canceled)
 25. A method for controlling a deployment rate of anairbag of a motor vehicle having a seat and a seat track assemblyincluding a stationary rail, a sensor disposed within the stationaryrail, a movable rail, and a shunt disposed within the movable rail, themethod comprising the steps of: sensing a magnetic field using thesensor and the shunt; producing a position signal indicating theposition of the seat based on the magnetic field sensed by the sensor;and varying the deployment rate of the airbag based upon the positionsignal.
 26. A method as set forth in claim 25 including the step ofsending the position signal to a controller during the step of varyingthe deployment rate of the airbag based upon the position signal.
 27. Amethod as set forth in claim 26 including the step of sending a controlsignal from the controller to an airbag controller during the step ofvarying the deployment rate of the airbag based upon the positionsignal.
 28. A method as set forth in claim 27 including the step ofsliding the shunt along the sensor during the step of sensing theposition of the sensor relative to the shunt.
 29. (canceled)